At the Tenth Ethylene Forum, May 10-12, 1995, Stone and Webster presented a paper on the concept of an integrated ethylene plant and one or more down stream chemical plants to react dilute ethylene or propylene to produce a product such as polyethylene or polypropylene and the unreacted stream of dilute ethylene or propylene would then be recycled back to the ethane cracker. The benefit from the concept was twofold:
a reduction in the capital cost and operating cost of the ethylene unit. PA1 a simple and cost effective way of debottlenecking existing ethylene units especially if already coupled to solution phase polyethylene units such as NOVA's SCLAIRTECH process. However, the paper failed to disclose high temperature ethylene furnaces or reactor materials to achieve high temperatures such as ceramic tubes or ceramic reactors. PA1 i) feeding a feedstock to a cracker operated at a maximum allowable tube wall temperature of from 1050.degree. C. to 1600.degree. C.; PA1 ii) passing the resulting product through a separation step to remove hydrocarbon streams having a carbon content of 3 and greater; PA1 iii) subjecting the resulting stream to a treatment to convert acetylene to ethylene; PA1 iv) removing the methane and hydrogen from the resulting stream to produce a product having an ethylene content from 75 weight % or more; PA1 v) feeding the resulting stream to a polymerization or oligomerization process which has an inherent high ethylene conversion per pass (i.e. greater than 85%) and can operate effectively at feed ethylene concentrations as low as 75 weight %, and polymerizing or oligomerizing the ethylene; and PA1 vi) separating the unpolymerized stream from the polymer and solvent, and returning it to the ethylene unit.
In addition to the Stone and Webster paper, U.S. Pat. No. 5,430,211 issued Jul. 4, 1995 assigned to the Dow Chemical Company teaches the use of dilute ethylene produced using catalytic cracking to produce ethyl benzene. The patent is restricted to the use of catalytically dehydrogenated dilute ethylene.
U.S. Pat. No. 5,488,148 issued Jan. 30, 1996 assigned to the Vista Chemical Company claims the use of dilute ethylene in making sulfonated alkyl compounds.
Chapter 17, "Steamless Pyrolysis of Ethane to Ethylene" by Y. Sony, L. T. Velenyi, A. A. Leff, W. R. Kliewer and J. E. Metcalf (in the text Novel Production Methods for Ethylene, Light Hydrocarbons and Aromatics edited by L. F. Albright et al, Marcel Decker, Inc. N.Y. (1992)), teaches the high temperature cracking of ethane in ceramic furnace tubes, preferably silicon carbide at high temperatures.
None of the above art teaches an integrated high temperature cracking process to produce a 75 weight % ethylene feedstock integrated with a polymerization and/or oligomerization process or both together in parallel trains. Alpha olefins from oligomerization could be used directly as comonomers for polyethylene production.